1. Field of the Invention
The present invention relates to a sheet material feeding apparatus which can be applied to image forming apparatuses, such as printers, copying machines and facsimiles, and to an image forming apparatus having the sheet material feeding apparatus.
2. Description of the Related Art
Existing image forming apparatuses or printing apparatuses, such as printers, copying machines and facsimiles, have been using as print medium sheet materials that include plain papers, thick papers such as postcards and envelopes, and special sheet materials such as plastic thin plates. Feeding sheet materials to such apparatuses is performed either manually one sheet at a time or automatically and/or continuously by a sheet material feeding apparatus.
The sheet material feeding apparatus comprises, for example, a pressure plate on which to stack a sheet material, a feeding roller to feed the sheet material from the pressure plate, and a movable guide member to regulate the position and direction of the sheet material mounted on the pressure plate. The pressure plate is normally located at a standby position from which the sheet material is not fed. To feed the sheet material, the pressure plate is moved to a feeding position where it engages the feeding roller.
An example of such a sheet material feeding apparatus is disclosed in Japanese Patent Laid-Open No. 2004-075356. In the sheet material feeding apparatus of Japanese Patent Laid-Open No. 2004-075356, a roulette unit is provided on a sheet material stacking surface of the pressure plate and a roulette engagement unit adapted to engage the roulette unit is provided on a slide surface of the guide member. With these units engaged, the guide member is held at a position corresponding to the size of the sheet material. These units are disengaged by an operator pushing an operation unit on the guide member, allowing the guide member to be moved.
In the sheet material feeding apparatus described above, it is desired that the guide member be made operable with optimal force, e.g. small force, when moving the guide member relative to the pressure plate to a position that matches the size of the sheet material. When the guide member has been moved to a desired position, it is also desired that an optimal holding force be applied between the guide member and the pressure plate to hold the guide member at that position. In feeding a sheet material, it is further desired that the guide member be firmly held to the pressure plate so that it will not be moved by the sheet material feeding operation.